/Engine/Source/Runtime/Slate/Public/Widgets/Layout/SFxWidget.h
This widget was created before render transforms existed for each widget, and it chose to apply the render transform AFTER the layout transform. This means leveraging the render transform ofFGeometrywould be expensive, as we would need to use Concat(LayoutTransform, RenderTransform, Inverse(LayoutTransform). Instead, we maintain the old way of doing it by modifying the AllottedGeometry only during rendering to append the widget's implied RenderTransform to the existing LayoutTransform.
virtual int32 OnPaint ( const [FPaintArgs](API\Runtime\SlateCore\Types\FPaintArgs) & Args, const [FGeometry](API\Runtime\SlateCore\Layout\FGeometry) & AllottedGeometry, const [FSlateRect](API\Runtime\SlateCore\Layout\FSlateRect) & MyCullingRect, [FSlateWindowElementList](API\Runtime\SlateCore\Rendering\FSlateWindowElementList) & OutDrawElements, int32 LayerId, const [FWidgetStyle](API\Runtime\SlateCore\Styling\FWidgetStyle) & InWidgetStyle, bool bParentEnabled ) const